1. Field of the Invention
The present invention relates to cordless telephones under the digital European cordless telephone (DECT) standard. More particularly, the present invention relates to a method for controlling the synchronization between a plurality of handset units and a base unit of the DECT standard in which each handset unit and the base unit are provided with different communication channel according to different manufacturers.
2. Description of the Related Art
Cordless telephone sets under the DECT (Digital European Cordless Telecommunication) Standard are known to have a base station that has both a normal telephone unit and an additional mobile unit. If the base station is integrated into a normal telephone unit or any additional mobile unit, a hand-free function can be achieved. A method for synchronizing a conventional DECT is characterized in that a dummy channel, which is predetermined by the manufacturer, is used to synchronize to a base station. However, the handset often loses synchronization with the base unit due to the interference caused by an additional handset integrated to the same base station. That is, the traffic channel of the additional handset, which is made by different manufacturer, is inadvertently allocated too close to or in the same channel range as the dummy channel assigned to the normal handset.
As an example, a base unit and a normal handset unit, which are manufactured by a German company, SIEMENS (trademark of Siemens Company), and an additional handset unit, which is made by a Korean company, SAMSUNG ELECTRONICS (trademark of Samsung Electronic Co., Ltd), can be integrated to the same base station. Each respective handset is pre-assigned with a dummy channel and a traffic channel at different frequency range according to their respective manufacturers. If the SAMSUNG handset is integrated to the base station and the SIEMENS handset attempts to establish a call set up, the SIEMENS hand set will be unable to establish a call set up using the original dummy channel assigned thereto. This problem occurs as the traffic channel assigned by the SAMSUNG handset is interfering with the dummy channel assigned between the handset and the base station made by the SIEMENS. Thus, the presence of SAMSUNG handset integrated to the same base station will interfere with the dummy channel, which is pre-assigned to the SIEMENS handset, when attempting a call set up. In such scenario, the SIEMENDS handset will keep on looking for the dummy channel, causing an increase in the power consumption. Currently, the prior art system does not address the above problem, thus the handset would be unable to synchronize to the base station timing due to the interference caused by the additional handset.
It is an object of the present invention to provide a method for controlling the synchronization of a DECT (digital European cordless telephone) in order to maintain the synchronization between additional handsets and a base unit made by different manufacturers.
It is another object of the present invention to provide a method for controlling the synchronization of a digital European cordless telephone (DECT) in order to prevent the unnecessary power consumption by the handset in an attempt to synchronize to the base unit timing.
According to an aspect of the present invention, a method for controlling the synchronization of additional digital European cordless telephones (DECTs) to a base unit includes the steps of: transmitting a new bearer information through a dummy bearer channel from the base unit to the handset unit if an additional handset is integrated to the same base unit, causing an interference with the dummy channel of the handset unit; storing the received bearer information into a candidate buffer of the handset unit; changing, by the handset, the receiving position of the dummy information to the information stored in the candidate buffer in the event that the cyclic redundancy checking (CRC) error exceeds a predetermined number of times; and, retrieving the new bearer information from the candidate buffer.
According to another aspect of the present invention, a method for controlling the synchronization of additional digital European cordless telephones (DECTs) to a base unit includes the steps of: synchronizing the base unit to a handset via a dummy channel; transmitting a new dummy bearer channel information from the base unit to a handset if a traffic channel is established between the base unit and an additional handset; storing the new bearer channel information into a candidate buffer of the handset; determining whether the dummy channel and the traffic channel coexists more than a predetermined time period; assigning a new dummy channel using the new dummy bearer channel information transmitted from the base unit if the dummy channel and the traffic channel coexists more than the predetermined time period; determining whether cyclic redundancy checking (CRC) errors of the dummy channel occurs more than a predefined number of times if the dummy channel and the traffic channel coexist less than the predetermined time period; and, assigning a new dummy channel using the new dummy bearer channel information transmitted from the base station if said CRC errors exceed the predefined number of times.
According to one aspect of the present invention, the method further includes the step of transmitting signal packet, which includes error detection information for detecting corrupt signals, as set forth under the DECT standard.
According to another aspect of the present invention, the method further includes the step of storing a plurality of different dummy channels in the base unit, wherein the dummy channels are used to synchronize with the base unit.
The present invention will now be described more specifically with reference to the drawings attached only by way of example.